The present invention relates in general to heat exchangers and more specifically to a high fin density coil design utilizing precoated fin stock.
The use of fins attached to fluid containing tubes to dissipate heat from a contained liquid is well known. Generally, a series of tubes carry heated liquid and form a cooling system. The tubes have metal fins attached thereto which form heat dissipating means. The fins are typically made of aluminum or copper.
The fins may be elongated, thin strips of aluminum with the width and length of the fins depending upon the number, diameter and configuration of the tubes. Generally, the fins may be held in place by a force fit over the tubes or may be adhered to the tubes by solder.
In order to provide an aesthetically pleasing look, it has been found advantageous to provide a coating on surface of the fins. It has been observed that system performance problems occur due to the thermal resistance typically found on high fin density coil designs when conventional (full coat) precoated fin stock is used for coil construction. These problems are particularly prevalent when a coated fin stock is utilized on a high fin density, >17 FPI (fins per linear inch), and even more so when >20 FPI, in coil designs applicable to residential outdoor products.
It should be noted that low fin density coils (10-15 FPI) don't have as much or a significant amount of thermal resistance due to a coating on the fin stock. It is more important to deal with this problem for high fin density coils.
A problem associated with a uniform coating pattern is such that the pattern near the outer edges of the fin stock, because of the drawing operation within the fin die, results in coating material being forced within the collars and also produces fins having a bare fin edge that will have to be scrapped.